DESCRIPTION: During development, stem/progenitor cells replicate and differentiate into many lineages, which give rise to precise number and subtypes of cells. Defects in lineage development can cause severe developmental diseases. Currently, the state-of-the-art lineage analysis uses mosaic labeling techniques to study one or a few lineages at a time to avoid ambiguity. While the small number of highlighted cells can be investigated extensively, complications in the unlabeled adjacent lineages are hidden from analysis. The ability of unambiguously labeling large number of lineages in situ is highly desired, since it is extremely exhausting, if not impossible to use the available tools to study the precise spatial-temporal relationship of all related lineages in one animal. We propose to develop a two-photon compatible multispectral and subcellular-coding system (MACS), which permits unambiguous labeling of large number of cell lineages in the same animal. We will validate MACS by mapping all of the ~100 neural lineages in single Drosophila central brain and depict the developmental processes of all Drosophila embryo neural lineages precisely in space and time. If success, MACS can be easily adapt to other transgenic animal models, including fish, mouse and rat. MACS will create new opportunities in lineage studies, such as investigating lineage variations among individuals, and between hypomorphic alleles or different sex; as well as cell non-autonomous effects of gene mutations in stem/progenitor cells.